Burner control for air conditioning system



March 27,1956 H. c. SHAGALOFF BURNER CONTROL FOR AIR CONDITIONING SYSTEM Filed April 22, 1953 3 Sheets-Sheet 1 INVENTOR.

I l I l ATTORNEY March 27, 1956 H. c. SHAGALOFF 2,739,793

BURNER CONTROL FOR AIR CONDITIONING SYSTEM Filed April 22, 1953 3 Sheets-Sheet 2 ATTORNEY March 27, 1956 H. c. SHAGALOFF 2,739,793

BURNER CONTROL FOR AIR CONDITIONING SYSTEM Filed April 22, 1953 3 Sheets-Sheet 3 2 2, E a; J Z Z7 5: l 2; I l /E z- :"1 '64 r Q {@8 1 r l 70 L: .Lg J ..LF; 83' gflei h 45? 2% i L I CI v I #1 A? g 59 #62 INVENTOR.

BY fifivnJW 4;, ATTORNEY BURNER CONTROL FOR AIR CONDITIGNING SYSTEM Harry C. Shagalotf, Evansville, Ind., assignor to Servel, Inc., New York, N. Y., a corporation of Delaware Application April 22, 1953, Serial No. 350,413

13 Claims. (Cl. 257-3) The present invention relates to controls for heat operated apparatus such as an air conditioner, and more particularly to a control for operating such apparatus at different heating rates.

Heat operated air conditioning apparatus of the type illustrated and described in United States Letters Patent to Sven N. E. Andersson 2,469,142, issued May 3, 1949, and entitled Air Conditioning, has been extensively used for air conditioning residences, stores, restaurants and the like. Such apparatus comprises a heat exchange means located in a circulating air duct with means to supply either a heating medium to the heat exchange means to heat an enclosure in the winter, or supply cooling medium to the heat exchange means to cool the enclosure in the summer. The heating and cooling requirements in any particular locality vary with the particular climatic conditions but are rarely equal so that the apparatus is heated at different rates for heating and cooling operations, respectively. A stack control is usually provided when an oil burner is used as the source of heat, and may be used with other types of burners, to stop operation of the burner if the stack temperature does not increase within a predetermined period of time after starting the burner or if the stack temperature decreases during operation of the burner. Thus, when heat operated apparatus of the type indicated is shifted from a higher heat input rate to a lower heat input rate, the stack control may cut out the burner under certain operating conditions.

One of the objects of the present invention is to provide a control arrangement to operate a burner at different heating rates and delay operation of the burner when shifting from a higher to a lower heating rate for a period of time suflicient to allow the stack to cool below. its operating temperature at'the lower heating rate.

Another object is to provide a selective control of the type indicated for adjusting an oil burner to operate at different heating rates and having a timing arrangement to delay operation of the burner after shifting from operation at a higher to a lower heating rate.

Still another object is to provide a control of the type indicated which is relatively simple, economical to manufacture and install, and reliable in operation.

These and other objects will become more apparent from the following description and drawings in which like reference characters denote like parts throughout the several views. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and not a definition of the limitation of the invention, reference being had for this purpose to the appended claims. in the drawings:

Fig. 1 is a diagrammatic view of a heat operated air conditioning apparatus to which the control of the present invention may be applied;

Fig. 2 is a diagrammatic view of the electric control showing the circuits for controlling operation of the burner at different heating rates and the timing means 2,739,793 Patented Mar. 27, 1956 for delaying operation of the burner when shifting from a higher to a lower heating rate;

Fig. 3 is a view of the timing control circuits showing the thermostat actuated to start the burner for a heating operation;

Fig. 4 is a view similar to Fig. 3 showing the selective switch means actuated to shift from a heating operation to- Air conditioning apparatus For purposes of illustration, the invention is shown applied to an air conditioning apparatus for either heating or cooling an enclosure to be conditioned, but it will be understood that the invention may have other applications or may be appliedto other types of heating and cooling apparatus. The particular air conditioning apparatus to which the present invention is shown applied is generally similar to that illustrated and described in the Andersson patent, referred to above; Suffice it to state herein that the air conditioning apparatus comprises a duct 5 for receiving air from the enclosure 6 to r be conditioned and a duct '7 for delivering conditioned air to the enclosure.

The air to be conditioned is circulated through the ducts 5 and i in the direction indicated by arrows by means of an electric motor operated'blower 3. As the air flows through the duct 5 it is conditioned by elements therein comprising a filter 9, a cooling elemerit 10, a heating element 11 and a humidifier 12. The

cooling element 10 constitutes the evaporator of a heat operated absorption refrigeration system while the heating element 11 constitutes the radiator of a heating system. Both the refrigeration system and heating system are selectively supplied with a suitable heating medium,

such as steam, from any suitable source such as a boiler 13 as illustrated in Fig. 1. The steam from the boiler 13 is directed to either the refrigeration system or the heating system by conduit means including a selective valve 14, later to be described in detail.

The heat operated refrigeration system preferably is of the type described and claimed in United States Letters Patent 2,282,503 to A. R. Thomas et 211., issued May 12, 1942. Such a refrigeration system operates in a partial vacuum and utilizes water as a refrigerant and a salt solution as an absorbent. The refrigeration system comprises a generator 15, a condenser 16, the evaporator 10, an absorber 17, and a heat exchanger 18 interconnected to provide closed circuits for refrigerant and absorbent. The generator 15 comprises a series of upright tubes 19 connected at their lower end to an inlet chamber 20 and at their upper ends to a separating chamber 21. Surrounding the tubes 19 is a jacket 22 providing a heating chamber 23 therebetween. A conduit 24 connects the separating chamber 21 to one end of the condenser 16 for delivering refrigerant vapor thereto and the opposite end of the condenser is connected to the top of the evaporator 10 by a U-tube 25 through which liquefied refrigerant flows. The U-tube 25 provides a liquid trap for maintaining the difference in pressure between the condenser 16 and evaporator 10 which is balanced by a liquid column in the left-hand leg of the U-tube as viewed in Fig. 1. Headers 26 connect opposite ends of the evaporator 10 to the top of the absorber 17 and re- 0.9 frigerant vapor flows through the headers from the evaporator to the absorber.

Absorption solution from which refrigerant vapor has been expelled flows by gravity from the separating chamber 21 to the top of the absorber 17 in a path of flow including conduit 27, heat exchanger 18, and conduit 28. Absorption solution strong in refrigerant flows by gravity from the bottom of the absorber 17 to the chamber 20 at the base of the generator 15 in a path of flow including conduit 29, heat exchanger 18, and conduit 30. Condensate is drained from the heating chamber 23 of the generator 15 by a conduit 31 including a condensate return pump 31a and a vent tube 32 is connected to the jacket 22 of the generator 15 and to the heating element or radiator 11 at a point remote from the steam inlet.

The absorber l7 and condenser 16 are cooled by cooling water from any suitable source, such as a cooling tower 33, illustrated in Fig. 1 of the drawings. An electric motor driven fan 34 at the top of the cooling tower 33'produces a flow of air upwardly therethrough and an electric motor driven pump 35 at the bottom of the tower circulates cooled water through the absorber 17 and condenser 16 of the refrigeration system. The path of flow of the cooling water comprises a conduit 36, cooling coils 37 in the absorber 17, conduit 38, condenser 16, and conduit 39 back to the top of the cooling tower.

When heat is supplied to the heating chamber 23 of the generator 15, refrigerant vapor is expelled from absorbent and delivered to the condenser 16 'where it is liquefied. The liquefied refrigerant is supplied to the evaporator 10 through the U-tube 25 which provides a liquid trap and together with the liquid traps in conduits 28 and 29 between the absorber 17 and generator 15 maintain the difference in pressure in the system. 'Absorption of refrigerant vapor by the absorbent in the absorber so reduces the pressure in the evaporator 10 as to cause evaporation of refrigerant therein at low temperature to produce a refrigerating or cooling sheet.

The heating system comprises the radiator 11 and the conduit means including the diverter valve 14 connecting the radiator to the boiler 13.

The conduit means for directing steam to either the refrigeration system or heating system comprises a steam main 40 connected between the boiler 13 and an inlet port to the selector valve 14. A conduit 41 leads from the selector valve 14 to the heating chamber 23 of the generator 15 and a conduit 42 leads from the selector valve to the heating element or radiator 11. The selector valve 14 has a valve element 14a movable to one or the other of two positions to close one conduit 41 or 42 and open the other conduit. The valve element 14;: is actuated from one to the other of its two positions by an electric motor 43, link 44 and crank arm 45 connected to the movable valve element. The motor 43 is operable through 180 of movement as controlled by limit switches 87 and 88, see Fig. 2, as later described in detail. Thus, when the valve element 14a is actuated by the motor 43 to close the conduit 42, it provides a path of flow for steam from the boiler 13 through the main 40 and conduit 41 to the heating chamber 23 of the generator 15. When the valve element 14a is moved to the other of its two positions to close the conduit 41, it provides a path of flow for steam from the boiler 13 through the main 40 and conduit 42 to the heating element or radiator 11.

Boiler and burner The boiler 13 may be of any suitable type, such as the sectional boiler illustrated having a hood 46 enclosing the sections and a flue or stack 4-8 for exhausting the products of combustion. The boiler 13 may be heated by a fuel burner or burners 5t) adjustable to operate at. different heating rates. While the burner or burners 50 may take other forms, they are preferably in the form of a unitary oil burner to which the control-of the present invention is particularly adapted. The oil burner, per se,

is not novel in the present application, and is therefore.

trated embodiment the oil burner 50 operates at one capacity for a heating operation and at a different capacity for a cooling operation, and the oil burner is mechanically adjusted by the motor 43 operating through a Bowden wire connection 54. For example, the air conditioning apparatus may operate on heating with 180,000 B. t. u. input per hour, and on cooling with 120,000 B. t. u. input per hour. The oil burner 50 alsoincludes a conventional ignition mechanism, not shown.

Boiler 13 also has a conventional stack safetvdevice which cooperates with other elements to stop operation of the oil burner 50 if the stack temperature does not increase within a predetermined period of time after the oil burner is started or if the stack temperature decreases during operation of the oil burner, either condition indicating that the combustible mixture supplied by the burner is not burning. The safety device 55 'is illustrated in Figs. 1, 7 and 8 as comprising a well known type of stack switch having a helically wound bimetallic strip 56 with one end anchored to a casing 57 and its opposite end connected to a rotatable shaft 58. Shaft 58 has a frictional connection to a tilting carriage 59 mounting a mercury switch 60. Upon an increase in stack temperature, the bimetallic strip 56 turns shaft 58 to rock carriage 59 in one direction and tilt the mercury switch 60 to open circuit position and upon a decrease in stack temperature the strip rocks the carriage in the. opposite direction to tilt the mercury switch to circuit closing position. An increase or decrease in stack temperature of approximately 75 F. is required to tilt the mercury switch 60 from an open circuit to a closed circuit position, or vice versa, upon a trend in either direction, but the actual movement of the carriage 59 is limited by stops 6 1 and 62 after which the shaft 58 slips relative to the carriage. Thus, upon starting of the burner 50, themercury switch is tilted from a closed to an open circuit position if the stack temperature increases 75 F. within a predetermined period of time, and moves the switch 60 to circuit closing position upon a decrease in stack temperature of 75 F. from any temperature in the stack.

Cooling and heating controls An electric control arrangement is provided for adjusting the valve 14 and burner 50 of the apparatus to shift or cooling cycle responsive to a condition afiected by the apparatus.

The electric control circuits are shown in Figs. 2 to 4 and are similar to those illustrated in the Andersson patent, referred to above. The control comprises supply mains 63 and 64 from a source of alternating electric current and connected through a line switch 65 to the primary winding 66 of a step-down transformer 67. .In parallel with the primary winding 66 of the transformer 67 is a circuit for energizing the motor for the siren lating fan 8- comprising a conductor 68 connecting the main 63 to one side of the fan motor and a conductor 69 connecting the other side of the fan motor to the main .64. A relay switch 70 in conductor 68 controls the starting and stopping of fan 8. I

The motors for the cooling tower fan 34, cooling tower pump 35 and condensate return pump 31a are connected in parallel with one side connected to the main 63 by a conductor 71 and the opposite side connected to the main 64 by a conductor 72. A relay switch 73 -5 in conductor 71 controls the simultaneous starting and stopping of the cooling tower fan 34 and pump 35 and condensate return pump 31:;

The motor 53 of the oil burner 50 also is connected in parallel with the primary of the transformer 67 with one side connected to the main 63 by a conductor 74 and the opposite side connected to the main 64 by a conductor 72a. A relay switch 75 in conductor 72a controls the starting of the burner. The secondary 66a of the stepdown transformer 67 is connected by conductors T1 and T2 to various control circuits for the air conditioning apparatus. These various control circuits comprise a ventilating circuit V for initiating operation of the circulating fan 8 when energized, a cooling circuit C for adjusting the apparatus for a cooling operation when energized, a heating circuit H for adjusting the apparatus for a heating operation when energized and a burner circuit B energized simultaneously with either the cooling circuit C or heating circuit H for initiating operation of the burner 50 when energized.

The circuits H, C and B are controlled by selective switch means 76 and thermostatic switch means 77. Selective switch means 76 comprises a three pole double throw switch operable in one position to adjust the apparatus for a heating operation and in the other position to adjust the apparatus for a cooling operation. With the selective switch means 76 in the upper heating position illustrated in Fig. 2, poles D, E and F engage fixed contacts D1, E1 and F1 and in the lower cooling position illustrated in Fig. 4 engage the fixed contacts D2, E2 and F2.

The thermostatic switch 77 comprises a single pole double throw switch having a pole G engageable with fixed contacts G1 or G2, respectively. Pole G is actuated into engagement with the fixed contact G2 upon an increase in temperature by a thermal responsive actuator 78 and is operated into engagement with the contact G1 upon a decrease in temperature by a spring 80 opposing the actuator. The thermal responsive actuator 78 is illustrated in the form of an expansible bellows connected to a sensing bulb 79 in the enclosure 6 to be conditioned and containing a volatile liquid for producing a pressure in the bellows corresponding to the temperature in the enclosure.

Conductor T1 from the secondary 66a of transformer 67 is connected to poles G and F of switch means 77 and 76, respectively, by means of conductors S1 and 82. Contact G1 of the thermostatic switch 77 is connected to the fixed contact Dr of the selective switch means 76 while contact G2 is connected to the fixed contact D2 of the selective switch means. Poles D and E of the selective switch means 76 are connected by a jumper 83 which, in turn, is connected to the conductor 13 of the burner circuit. Fixed contact E1 is connected to conductor H of the heating circuit and fixed contact E2 is connected to contact H1 of a ventilating control switch 84, later to be described, by a conductor 85. Fixed contact P2 of selective switch means 76 is connected to conductor C of the cooling circuit.

Ventilating switch 84 is a single pole double throw type having its' pole H connected to conductor V of the ventilating circuit and fixed contacts H2 connected to T1. Fixed contact H2 also is connected to conductor T2 through a resistance heating element 86 to the opposite side of transformer secondary 66a. Heating element 86 maintains the bellows 78 of the thermostat at a higher temperature than the bulb 79. Thus, when continuous ventilation is desired, switch 84 is actuated to engage pole H with contact H2. When heating is desired pole H of switch 84 is actuated to engage contact H1 and the three pole switch 76 is actuated to the upper position shown in Fig. 2. Upon a decrease in temperature, pole G of the thermostatic switch 77 is actuated into engagement with contact G1 to energize the burner and heating circuits B and H. When cooling is desired, the three pole double throw switch 76 is moved to the lower position illustrated in Fig. 4 to immediately energize the cooling circuit C and upon an increase in temperaturev pole G is actuated into engagement with contact G2 to energize the burner circuit B. 1

The cooling and heating circuits C and H are connected to the electric motor 43 for actuating the valve element 14a of the selective valve 14 from one to the other of two positions. Operation of the motor 43 is controlled by limit switches 87 and 88 for connecting the conductor C or H, respectively to the winding 89 of the motor. A third limit switch 90 is provided for short-circuiting a low temperature cutout switch 91 on heating, as later described. An electromagnetic valve 92 for controlling the supply of water to the humidifier 12 is also connected to the conductor H of the heating circuit. The circuits from the winding of the valve actuator 92 and motor winding 89 are completed through a common return conductor 93 including the low temperature cutout switch 91 responsive to the temperature of the cooling element 10, vent switch 94 responsive to the venting of steam from the generator 15 or heating element 11 or overflow of condensate in the condensate return pump 31a and the low water control switch 95 responsive to the level of water in the boiler 13, see Fig. 1, and back to the conductor T2. The limit switch 90, referred to above, shortcircuits the low temperature cutout switch 91 during a heating operation but is moved to an open position by the motor 43 during a cooling operation. A makeup water valve 96 is actuated by the low water cutout switch 95 to supply makeup water to the boiler.

A thermally operated switch 97 for controlling operation of blower 8 and cooling tower a3 is also provided in the control. The switch 97 is a double pole double throw type having its pole I connected to the coil 98 for the blower relay switch 70 and the opposite end of the coil is connected by a conductor 99 to T2. Fixed contact 11 is connected to T1 through a conductor 100 and fixed contact 12 is connected to the conductor V of the ventilating circuit. Pole I of switch 97 is connected to one end of coil 10]. for actuating relay switch 73 for the cooling tower 33 and the opposite end of the coil is connected to the return conductor 93. Fixed contact 11 is connected to the conductor C of the cooling circuit by a conductor 102. Poles I and I of switch 97 normally take the lower position illustrated in 2 but are moved to an upper position by a thermal responsive element having an expansible bellows 103 and thermal sensing bulbs 104 and 104 adjacent the heating element 11 and generator 15, see Fig. 1. The bulbs 104- and 104' contain a volatile liquid for producing a pressure in the bellows when steam is supplied to the heating element 11 or generator 5, respectively. As thus far described, the electric control is substantially the same as that illustrated and described in the Andersson patent, referred to above.

Timing device In accordance with the present invention, a timing arrangement is provided in the control for delaying operation of the oil burner 50 when shifting from one conditioning operation at a higher heat input to another conditioning operation at a lower heat input. In the illustrated embodiment the timing device comprises a motor operated switching means controlled by the selective switching means 76 and, in turn, controlling the burner circuit B.

For the purpose of describing the relation of the timing device to the other elements of the control, the burner circuit B is completed through a switch 105 of the timing device, relay coil 106 and safety control switch 107 as illustrated in Fig. 2. Switch 105 of the timing device opens and closes the burner circuit B in a manner later to be described in detail. 106 actuates the oil burner control switch 75 to closed Relay coil 7 position when the burner circuit B is energized to initiate operation of the oil burner 50. Safety switch 107 has a bimetallic element which warps to open the burner circuit B when heated for a period of time. Bimetallic warp switch 107 is heated by an electric heating element 108 in a safety control circuit connected between T1 and return conductor 93 and including a relay switch 109 and the stack switch 60, previously described. Relay switch 109 is arranged to be actuated by the relay coil 106 in the burner circuit B and the heating element 108 is arranged in heat exchange relation to the bimetallic warp switch 107. The design of the heating element 103 and warp switch 167 is such that if the oil burner 50 operates for two minutes without actuating the thermal responsive stack switch 60 to open circuit position, the heating element. 103 will open the safety switch 107 in the burner circuit and stop operation of the oil burner 50. It will be observed that relay coil 106 in the burner circuit B actuates both relay switches 75 and 109 to start oil burner 50 and energize the safety control circuit S when the burner circuit is energized.

The motor operated switching means comprises the switch 105 in the burner circuit B, a pre-setting switch 110 movable from the energized circuit H or C to the other deenergized circuit for operation on the next shift of the selective switch means 76 and a holding relay 111 for maintaining the switch operating motor 112 energized to complete a cycle. Switch 105 is a single pole double throw type having its pole connected to the conductor B of the burner circuit and a fixed contact 113 connected to the relay coil 106. The other fixed contact 114 is connected to the holding relay 111. Thus, when the switch 105 is in the position illustrated in Fig. 2, the burner circuit B is completed and when moved to the position illustrated in Fig. 4 the burner circuit B is opened. Switch 110 is also a single pole double throw switch having one fixed contact 115 connected to the heating circuit H and the other fixed contact 116 connected to the cooling circuit C. The pole of switch 110 is connected to one of the poles of the holding relay 111.

In the illustrated embodiment, switches 105 and 110 are actuated by cams 117 and 115, respectively, which are driven by the electric motor 112. Cam 117 has two recesses 119 and 120, see Fig. 5, and lobes 121 and 122 between the recesses. A switch operator 123 rides on the surface of the earn 117 and when it enters recess 119 or 120, it moves the pole of switch 105 into engagement with contact 113 and when it rides on the lobes 121 and 122 it moves the pole of the switch into engagement with contact 114. Cam 118 has a recess 124 and a lobe 125. A switch operator 126 rides on the surface of the cam 118 and when in the recess 124 it moves the pole of switch 110 into engagement with contact 115 and when raised by the lobe it moves the pole into engagement with contact 116. It will be noted by reference to Fig. 5 that the recess 120 of earn 117 is aligned with recess 124 in cam 118 so that when switch 110 connects the heating circuit H, switch 105 closes burner circuit B, and recess 119 of earn 117 is aligned with lobe 125 of cam 118 so {that when switch 110 conmeets the cooling circuit C, switch 105 also closes the burner circuit B.

Theholding relay 111 comprises a double pole double throw switch and a relay coil 131. Motor 112 is energized from either the heating circuit 11 or cooling circui-t C connected to the fixed contacts 115 and 116 of switch 110. A circuit is completed to motor 112 from the pole of switch 110 through a conductor 132 to pole 133 of holding relay 11.1, conductors 135 and 13.6 to one side of the motor 112 and from the opposite side of motor through a conductor .137 to return conductor193 connected to T2. Energizatjion of motor 112 causes earn 117 1torotate and move pole of switch 105 into engagement with fixed contact 114 and open the ing relay 111 and fixed contact 139 is connected to the conductor 135 to complete a circuit through thc 'conductor 136 to the motor 112. Upon energiza'tionof the relay coil 131 through switch 105, the pole 138 is moved into engagement with contact '139 to complete a holding circuit from burner circuit B through pole 138 and conductors 135 and 136 to the motor 112. The holding circuit will then maintain operation of the motor 112 until the cam follower .123 enters a recess 119 or 120 in the earn 117 during which time the pressetting switch 110 will have been moved by cam ll s fro'm the energized circuit C or H to the other deenergized circuit. One form of the invention having now be'eii described in detail, the mode of operation is explained 'as follows:

Mode of operation For purposes of description, let it be assumed that the control elements are in the positions illustrated in Figs. 1 and 2, that is, with the selective switch 76, see Fig. 2, in the upper heating position, the diverter valve 14 in position to direct steam from boiler 13 to heating coil 11, the oil burner adjusted by the Bowden wire 54 to supply heat to the boiler 13 at the higher heating rate, switch 110 disconnected from the heating circuit H and connected to the cooling circuit C, switch 105'in engagement with contact 113 to connect relay (3011 106 for energization and the pole G of thermostatic switch 77 in engagement with contact G2 indicating that the temperature in the enclosure 6 is satisfactory. It also will be noted that limit switch 87 of janitor motor43 is open to disconnect its winding 89 from the heating circuit H, the limit switch 88 is closed to connect the cooling circuit C to the motor winding, and that motor 112 for actuating switches .105 and 1-10 is disconnected from the heating circuit and connected for energization by the cooling circuit C.

Upon a decrease in temperature in the enclosure 6, the pole G of thermostatic switch 77 is moved from the position illustrated in Fig. 2 into engagement with contact G1 by the spring 80 as illustrated in Fig. *3. The burner circuit B is then energized from T1 through condoctor 81, pole G, contact G1 to contact D1 of selective switch 76,, jumper 83, conductor B through switch 105, relay .coil 106, thermal warp switch 107 and return con ductor 93 to T2. Energization of the relay coil 1.06 closes relay switch 75 to start burner 50 and .relay switch 109 to energize the safety circuit S. The oil burner SO heats the boiler 13 to supply steam through the conduit 42 to the heating element .11. When the heating element becomes hot, thermal responsive bulb 104 acting through bellows 103 actuates switch 97 to engage pole fI with contact I1 to complete a circuit from Trtjhrou'gh coirductor 100, relay coil 98 and conductor 99 to T see Fig. 2. Energization of the coil 98 closes relay switch to initiate operation of the blower ,8 to circulate air from the enclosure 6 through the conduit 5 in contact with the heating .element 11 and then through the blower Sback to the enclosure.

The safety circuit S is completed fromTi through conductor S, relay switch 109, heating element osgsgsek switch .60 and return conductor 93 to T2. o eration .Of the oil burner 50 heats the thermal element "5.6 efihe stack safety device, to tilt the mercury switch .fitl to th'e open circuit position illustrated in Fig. 3. If the stack switch .60 has not opened after twominutes of operation of the oil burner 50, the heating element 108 will have opened the safety switch 107 in the burner circuit and deenergized the relay coil'106 to open relay switch and stop operation of the burner. Although not shown or described, a manual reset switching ariangemeiit is 9 usually provided to prevent further operation of the oil burner until the cause of the trouble has been discovered to prevent repeated cycling cf the oil burner. The thermostatic switch 77 is responsive to the temperature in the enclosure 6 as affected by the heating element 11 and operates to energize and deenergize the burner circuit B to maintain the temperature in the enclosure within predetermined limits.

When cooling is desired, the selective switch means 76 is operated from the upper heating position illustrated in Fig. 2 to the lower cooling position illustrated in Fig. 4. Immediately upon engagement of the pole F of selective switch 76 with contact F2, the cooling circuit is energized from T1 through conductors 81 and 82, pole F and contact F2 and conductor C of the cooling circuit. A circuit is completed from the conductor C through limit switch 88 of motor 43, motor winding 89 and return conductor 93 to T2. Energization of the motor winding 89 causes the crank and linkage mechanism,

see Fig. 1, to operate the valve element 14a of selector 9 valve 14 from the position shown in full lines in Fig. 1 to the position indicated in dotted lines to close the conduit 42 to the heating element 11 and open the conduit 41 to the generator 15 of the heat operated refrigeration system. Rotation of the motor 43 acting through the Bowden wire connection 54 adjusts the oil burner 50 to heat the boiler 13 at a lower heating rate. Rotation of the motor 43 also actuates the limit switches 87 and 88 to open the circuit from the conductor C through the motor winding 89 to stop the motor and connect the deenergized heating conductor H to the motor winding.

Simultaneously, a circuit is made from the conductor C of the cooling circuit through switch 110, see Fig. 2, conductor 132, pole 133 of the holding relay 111 and conductors 135 and 136 to motor 112, and the circuit from the motor is completed through the conductor 137 and return conductor 93 to T2. Energization of the motor 112 causes rotation of the cams 117 and 118 counterclockwise, see Figs. 2 and 4. Upon initial rotation of cam 117, the lobe portion 121 actuates the switch operator 123 to move the pole of switch 105 from'engagement with contact 113 into engagement with contact 114. Switch 105 thereby opens-the burner circuit B to prevent operation of the burner 50 and completes a circuit through the relay coil 131 of holding relay 111 and return conductor 93 to T2. Energization of relay coil 131 simultaneously moves the pole 133 of holding relay 111 to open position and pole 138 into engagement with contact 139 'so as to make a holding circuit from conductor B through switches 105 and 138 and conductors 135 and 136 to motor 112. The motor 112 continues tobe operated through the holding circuit until the switch operator 123 rides into the recess 120 in the cam 121 to move the pole of "switch 105 from contact 114 back into engagement with the contact 113. Prior to the operation of the switch '105 the cam 118 will have operated the pole of the presetting switch 110 from engagement with the contact 116 in the cooling circuit C into engagement with contact 115 connected to the deenergized heating circuit H. Thus, actuation of the switch 105 from the position illustrated in Fig. 4 to the position illustrated in Fig. 2 deenergizes the holding circuit and stops the motor 112 and simultaneously connects the burner circuit B for-energization. The motor 112 is so designed and geared as to require four minutes to rotate from recess 119 to recess 120 relative to switch operator 123 when shifting from heating to cooling during which time the relay coil 106 is deener'gized to prevent operation of the burner 50. This four-minute delay has been found sufiicient to permit the stackto cool from the operating stack temperature at the higher heating rate for heating to the operating stack temperature at the lower heating rate for cooling. Thus, after the four-minute delay, operation of the oil burner 50 will cause the stack switch 60 to be opened by an increase in stack temperature and prevent the bimetallic warp switch '107 from opening the burner circuit whenshifting from heating to cooling.

' After the timing arrangement, above described, delays.

operation of the oil burner 50 for four minutes, the thermostatic switch 77 may initiate operation of: the apparatus on a cooling cycle. If pole G of thermostatic switch 77 has engaged contact G2 during the four minute delay period, or after the delay period, a circuit is com-. pleted from T1 through conductor 81, pole G and contact G2 of switch 77 to contact D2 and pole D of selectiveswitch 76, jumper 83, conductor B, switch 105, relay coil 106, thermal warp switch 107 and return conductor 93 to T2 to initiate operation of the oil burner 50 and energization of the safety circuit S in the manner previously described.

Simultaneous with operation of burner 50, a circuit is made from the jumper 83 through pole E and contact E2 of selective switch 76 and through conductor 85 to contact H1 of the ventilating switch 84. From the pole H of the ventilating switch 84 the circuit is completed through the conductor V of the ventilating circuit and pole I of the switch 97 through relay coil 98 and conductor 99 to T2. Energization of the relay 98 closes relay switch 70 to initiate operation of the blower 8. Thus, on a cooling cycle, operation of the blower 8 is immediately initiated upon engagement of the pole G of thermostatic switch 77 with the fixed contact G2. When steam is supplied to the generator 15, the thermostatic switch 97 is actuated to engage the pole I with the contact Ii to complete a circuit from T1 through conductor 100, pole I, relay coil 98 and a conductor 99 to T2 to maintain the blower 8 in operation as long as steam is supplied to the generator. Pole 1 of switch 97 engages contact J1 to complete a circuit from conductor C of the cooling circuit through the conductor 102, pole J and relay coil 101 and return conductor 93 to T2. Energization of the relay coil 101 closes relay switch 73 to initiate operation of the cooling tower fan 34, cooling tower pump 35 and condensate return pump 31a. Heating of generator 15 of the heat operated refrigeration system causes refrigerant to be supplied to the cooling element 10 to cool the air circulated by the blower 8. The apparatus then operates intermittently on cooling as controlled by the thermostatic switch 77 to maintain the enclosure 6 at the desired temperature.

When the selective switch means 76 is again shifted from the lower cooling position illustrated in Fig. 4 to the upper heating position illustrated in Fig. 2, a circuit will he completed from the heating circuit H through the switch 110 of the timing arrangement to initiate operation of the motor 112 in the manner previously described and the motor operating through the cams 117 and 118 returns the switches and to the position illustrated in Fig. 2. While no delay is required when shifting from a'cooling operation at a lower heating rate to a heating operation at a higher heating rate, the apparatus does cause some delay in order to reset the timing apparatus. Inthe illustrated arrangement the lobe 121 for delaying operation of the oil burner 50 when shifting from heating to cooling delays operation of the oil burner for four minutes while the lobe 122 between the recesses 119 and 120, see Fig. 5, delays operation of the burner for only one minute to give sufiicient time for the cam 118 to reset the switch 110.

Automatic shift-over Fig. 6 illustrates a modified arrangement for automati caliy shifting from a heating operation to a cooling opera zt ion and vice versa. In the modified arrangement the selective switch means 76 is combined with the thermostatic switch means 77 of Figs. 2 to 4. V

The modified arrangement is generally similar to that illustratedand described in my prior Patent 2,610,032 issued September 9, 1952, and entitled Air Conditioning. The arrangement comprises a double pole double throw burner for a suflicient period to allow the safety device to cool below the stack operating temperature at the lower heating rate.

5. In a heat operated apparatus, a burner for heating the apparatus, means for adjusting the burner to operate at different heating rates, a thermostat responsive to a condition afiected by said apparatus to start operation of the burner, and a timing device operatively associated with said adjusting means and thermostat to delay starting of the burner by the thermostat for a predetermined period of time after the burner has been adjusted from one heating rate to another.

6. In a heat operated apparatus a burner for heating the apparatus, means for adjusting the burner to operate at different heating rates, an electric control comprising selective switch means for initiating operation of the burner adjusting means, said electric control including a thermostatic switch responsive to a condition affected by the apparatus and connected to start and stop the burner at the selected heat rate, and a timing device operatively associated with the selective switch means and having switch means to delay starting of the burner by the thermostatic switch for a predetermined period of time after the burner has been adjusted from a higher to a lower heating rate.

7. In a heat operated apparatus according to claim 6 in which the electric control includes a stack switch responsive to a decrease in the stack temperature of the flue gas products to stop operation of the burner, and said timing device being connected to delay operation of the burner until the stack has cooled to the operating temperature at the lower heating rate.

8. In a heat operated apparatus according to claim 6 in which the timing switch means comprises a rotatable element for closing a circuit after a predetermined period of rotation, and an electric motor energized by the selective switch means for turning the rotatable element.

9. In a heat operated apparatus according to claim 6 in which the electric control comprises a heating circuit 14 and a cooling circuit connected for energization by the selective switch means, and a burner circuit connected for energization by the thermostatic switch and including the timing switch means.

10. In a heat operated apparatus according to claim 9 in which the timing switch means comprises a cam operated switch in the burner circuit, an electric motor for actuating the cam operated switch, and a second cam switch operated by the motor for connecting the heating circuit or cooling circuit to the motor.

11. In a heat operated apparatus according to claim 9 in which the burner is an oil burner, electrically operated means connected to adjust the oil burner to operate at different heating rates, said last named means being connected to the control means for operation to different positions by the heating and cooling circuits, respectively, when energized by the selective switch means.

12. In a heat operated apparatus according to claim 9 in which the selective switch means is manually operated to connect the heating or cooling circuits for energization.

13. In a heat operated apparatus according to claim 9 in which the selective switch means is thermostatically operated.

References Cited in the file of this patent UNITED STATES PATENTS 1,860,311 Klees May 24, 1932 2,016,805 Kinnan Oct. 8, 1935 2,342,126 Dicke Feb. 22, 1944 2,358,809 Jennings Sept. 26, 1944 2,464,700 Logan Mar. 15, 1949 2,469,142 Andersson May 3, 1949 2,474,595 Richardson June 8, 1949 2,504,250 Cochrane Apr. 18, 1950 2,551,927 Charles May 8, 1951 2,581,122 McNeely Jan. 1, 1952 2,610,032 Shagalofi Sept. 9, 1952 2,634,805 Bills et al Apr. 14, 1953 2,655,208 Outterson Oct. 13, 1953 

